Calling Object Method From Another Object
Oct 26, 2014
I've been trying to learn Java for the last 36 hours or so (after applying for a HTML/CSS job saying "Java knowledge preferred"), and decided to experiment a bit making a graphical tic-tac-toe game. I eventually managed to get that done and it's working. Working code below:
[Java] tic tac toe 1 - Pastebin
So, it works to an extent, however, the way I am capturing which cell is selected seems very sloppy, and would not work if the cells weren't squares or rectangles. So I made a copy of the project and restructured it adding the mouse event to the cells, but now I can't get JComponent to repaint. New code below:
tic tac toe 2 - Pastebin
Curiously, clicking triggers the action for all 9 cells, but I presume it's because I haven't bounded them making it think I've clicked all 9 simultaneously.
What I've tried:
Make the Cell class extend the game class and call this.repaint()- causes stack overflow.
Calling Game.GameState() within the cell clicking event and making that function static - compiler doesn't like calling repaint() inside a static function.
Making another class to make a clone of the Game object and then refresh- was never going to work....
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Oct 27, 2014
I have a class for employees. This class has basic information for the employee but no real pay information. And 2 subclasses, one for employee's paid for hourly rates and one for those paid a yearly salary. Each subclass has their own pay() method, that calculates and returns their pay and extra fields relative to calculate that.
I'm just curious, if I do this and create an object for an hourly paid employee like so:
Object hourly1 = new HourlyEmployeeWilson("John Doe", "123 Tech Street",361961,"Human Resources", 0,12.50,50);
How can I utilize that classes public method of pay() to gather this instance (or hourly paid employee)'s pay? I've tried doing so via:
System.out.println(hourly1.pay());
But I get
DriverPayWilson.java:9: error: cannot find symbol
System.out.println(hourly1.pay());
^
symbol: method pay()
location: variable hourly1 of type Object
1 error
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Oct 26, 2014
When I try to call an object it can't find the symbol in the argument list. NetBeans says that it cannot find the movieCategory symbol when I try to call it. When I compile it to test a popup comes up that states "One or more projects were compiled with errors. Application you are running may end unexpectedly. I ran it anyways and everything runs up to the point of where it should call the object.
At this point it should get the Movie object and run the code within that, but if I put one of the categories it throws. "Exception in thread "main" java. lang.RuntimeException: Uncompilable source code - Erroneous tree type: <any>at MovieApp.main(MovieApp.java:33)Java Result: 1"
From my understanding to call an object it requires objectName.methodName(argumentList). Here is my Main method
/**
*This application will store a list of 100 movies and display them by category
*/
import java.util.Scanner;
public class MovieApp
{
public static void main(String args[])
{
//Displays <code>String</code> welcome message
System.out.println("Welcome to the Movie Application.");
System.out.println("There are 100 movies in the list.");
System.out.println("What category are you interested in?");
System.out.println();
[code].....
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Jun 14, 2014
Say I have two classes, Author and Book, and I have 2 author objects and 10 book objects. I would like to know how to do two things:
1) Make some sort of connection that makes clear that author X wrote books A, B and F.
2) Call a method from a book object that is connected to an author.
Seeing as I don't know which books will be connected to an author, is there some way to call a method of an object bases on a variable object name? Something like call the getFirstPage() method for every book that is linked to author X?
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Mar 28, 2014
Create an equals method that takes an object reference and returns true if the given object equals this object.
Hint: You'll need 'instanceof' and cast to a (Geocache)
So far I have:
public boolean equals(Object O){
if(O instanceof Geocache){
Geocache j=(Geocache) O;
if (this.equals(j)) //I know this is wrong... but I can't figure it out
return true;
}
else return false;
}
I think I have it correct up to the casting but I don't understand what I'm suppose to do with the this.equals(). Also I'm getting an error that I'm not returning a boolean... I get this all the time in other problems. I don't get why since I have to instances of returning booleans in this. "returns true if the given object equals this object" makes no sense to me. I assume the given object, in my case, is 'O'. What is 'this' object referring to?
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May 20, 2015
In the process of creating a new class, I need to move my main method from the class SaveDate to the class DynamicTest. Below I have listed the code of both classes.The objective is to be able to run my program from the DynamicTest Class. I need understanding the process of moving my main method to a different class and creating an Object of a class and calling its method.
public class SaveData {
private static final Map<String, Object> myCachedTreeMap = new TreeMap<String, Object>();
public static final List<String> getLines(final String resourceParam, final Charset charset) throws IOException{
System.out.println("Please get: "+resourceParam);
if (myCachedTreeMap.containsKey(resourceParam) ) {
// Use the cached file, to prevent an additional read.
[Code] ......
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Apr 6, 2015
How do I take the union between an object called on and the object passed in the parameter?I have an interface:
Java Code:
import java.util.Set;
/**
* An extended Set where additional functionality is added
*/
public interface NewSet<T> extends Set<T> {
[code]...
Now, the union method requires a NewSet object to be called on. The Union will be performed between the object called on and the object passed in the parameter, which is set.How do I call on a NewSet object in order to take the union between the object called on and the object passed in?Do I just do:
Java Code:
public NewSet<T> union(NewSet<T> set) {
NewSet<T> calledOn = new ArrayList<T>();
// ...
} mh_sh_highlight_all('java');
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Feb 14, 2014
I have some class called sorted to sort the linked list through the nodes of the list. and other class to test this ability, i made object of the sort class called "list1" and insert the values to the linked list.
If i make other object called "list2" and want to merge those two lists by using method merge in sort class. And wrote code of
list1.merge(list2);
How can the merge method in sort class know the values of list1 that called it as this object is created in other class.
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Oct 7, 2014
I am new to Java and have read books, the Java docs, and searched the Internet for my problem to no avail. I have an Array of objects that contains strings. How can I get the object's strings to print in a list so that the user can select that object to manipulate its attributes? For example, the user can select "Guitar 1" from a list and manipulate its attributes like tuning it, playing it, etc. I have a class called Instruments and created 10 guitar objects.Here is the code:
Instrument [] guitar = new Instrument[10];
for (int i = 0; i < 10; i++) {
guitar[0] = new Instrument("Guitar 1");
guitar[1] = new Instrument("Guitar 2");
guitar[2] = new Instrument("Guitar 3");
guitar[3] = new Instrument("Guitar 4");
guitar[4] = new Instrument("Guitar 5");
guitar[5] = new Instrument("Guitar 6");
[code]...
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Mar 27, 2015
can a keyevent in java make the space ship and the laser too ?
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Apr 15, 2014
For example I create an object like this:
BankAccount b = new SavingsAccount();
Now lets say that I want to access a method 'addInterest()' that is in the 'SavingsAccount' class I would have to do: '((SavingsAccount)s).addInterest();'
The question I have is why do I have to cast 'b' to SavingsAccount? Isn't the actual object reference of 'b' already an instance of 'SavingsAccount' class? How does the 'BankAccount' affect the object itself? I'm really confused as to what class is truly getting instantiated and how BankAccount and SavingsAccount are both functioning to make the object 'b'.
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Nov 6, 2014
I don't understand why the object reference variable 'a' cannot be recast from a thisA object reference to a thisB object reference.Is it the case that once a reference variable is linked to a particular object type then it cannot switch object types later on.I am facing the Java Associate Developer exam soon and I am just clearing up some issues in my head around object reference variable assignment,
class thisA {}
class thisB extends thisA { String testString = "test";}
public class CastQuestion2 {
public static void main(String[] args) {
thisA a = new thisA();
thisB b = new thisB();
[code]....
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Nov 19, 2014
I am trying to get this to where I can type in a name and it will search through each object and print back the corresponding object info.
Java Code:
import java.util.Scanner;
public class MyPeople {
public static void main(String[] args) {
Person[] p = new Person[] {
new Person("Chris", 26, "Male", "NJ", "Single"),
new Person("JoAnna", 23, "Female", "NJ", "Single"),
new Person("Dana", 24, "Female", "NJ", "Single"),
new Person("Dan", 25, "Male", "NJ", "Single"),
new Person("Mike", 31, "Male", "NJ", "Married") };
[code]....
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Apr 9, 2014
Task:The main method of the class Things below creates an object called printer deriving from the class PrintingClass and uses that object to print text. Your task is to write the PrintingClass class.
Program to complete:
import java.util.Scanner;
public class Things {
public static void main(String args[]) {
String characterString;
Scanner reader = new Scanner(System.in);
PrintingClass printer = new PrintingClass();
System.out.print("Type in the character string for printing: ");
characterString = reader.nextLine();
printer.Print(characterString);
}
}
// Write the missing class here
Note: In this exercise the solution is part of a conversion unit where many classes have been declared. Because of this the classes are not declared as public using the public attribute.
Example output
Type in the character string for printing: John Doe
John Doe
My Class:
class PrintingClass {
public void print(){
System.out.println(characterString);
}
}
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Mar 5, 2014
Which method is used while passing or returning a java object from the native method?
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Mar 23, 2015
If I set a Jlist to contain an array of objects, how can I display properties of each object instead of the object array list itself. Ex:
Instead of:
Person1
Person2
Person3
display values such as each person name within the Jlist:
Mike
Paul
Andrew
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Nov 19, 2014
I have just started working with linked lists. I have a linked list of Objects and I want to be able to search for a specific object. But currently my code continues to return false. Also how would I go about removing the first index of the linked list.
public static void main(String[] args) {
LinkedList<Cookies> ml = new LinkedList<>();
int choice = 0;
while (choice >= 0) {
choice = menu();
[Code] ....
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Dec 27, 2014
I am reading Head First: Java and got to Object References. In the book I got a little bit confused on what happens when two object reference's point at the same object so I wrote a small crude test, the below code. This of course clarified what happens but what I am interested in knowing is in what circumstances would you want to have two separate references for the same object when you could just use the original? Eg. v1
class ObjectValue{
int objVal = 1;
}
class ObjectValueTestDrive{
public static void main(String [] args){
// "Value of v# should be" refers to if it copied the given object values, instead of referencing the same object
ObjectValue v1 = new ObjectValue();
System.out.println("Value of v1 should be 1:" + " "+ v1.objVal);
[code]....
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Aug 18, 2014
Explain anonymous objects with example clearly...i read some where anonymous objects advantage is saving memory...it is benificiable when there is only one time object usage in our program..i can't understand one time usage of object ....i know anonymous objects but i don't know in which context we use them in our programs...i did the anonymous object program with my own example but i can't differentiate this one with normal object..i'm providing my own example below
//anonymous object
public class anonymous {
int x=10;
int y=25;
void display()
{
System.out.println("anomymous");
[code]....
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Jan 15, 2015
What I want to do is have a label that is updated whenever an object gets some new, relevant data.The way you do it in Java looks different from the way we do it in Objective-C. In Objective-C, we have what's known as a protocol. An Objective-C protocol is almost exactly like a Java "implementation." In Obj-C, if I want the user to see the address of where he is, I can have an object that gets the information and invokes a view controller's method; at that point, the view controller would then take the data passed to it and display the data in a label. However, the view controller is an instance of a subclass of the bundled view controller class.
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Jun 11, 2014
I am trying to find either some references to point me on the right track with passing an object with all of it's properties still in tact after it's been created. Currently I am trying to do this through an interface but it seems to just create a new object everytime without the properties. Example below :
import java.util.ArrayList;
import java.util.List;
public interface TPerson{
//public Person p = null;
}
class Thrower {
Person p;
[code]....
When I implement the interface on the other objects as soon as I call the setP method shown above it seems to just create a new one even though I pass the object to the method I want to use.
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Mar 7, 2014
I read the following comment at stackoverflow.com. It is not clear to me why equals in the code below does not override - i looked up Object class equals() and the signature is same.
public class Foo {
private String id;
public boolean equals(Foo f) { return id.equals(f.id);}
}
This class compiles as written, but adding the @Override tag to the equals method will cause a compilation error as it does not override the equals method on Object.
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Jul 20, 2014
I am getting this error "Type mismatch: cannot convert from Object to E" in the last line of the pop() method.
package stack;
public class Node<E> {
E item;
Node next;
Node(E item) {
this.item = item;
this.next = null;
}
[code]....
I don't understand why that error occurs despite item being declared as type E in the Node class.
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Nov 1, 2005
I don't know why class Object have two PROTECTED method -- clone() and finalize(). And in JUnit's source code, I notice that kent write :public class AClass extends Object {}I really don't understand what diffrient frompublic class AClass {}
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Jul 25, 2014
Which two method HashMap key object should implement?..
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Oct 29, 2014
I am working on an independent project it is a simple little text based rpg that will run in a counsel window. I have an object for Character that is creating during a CreateCharacter method. I want the play to be able to enter a character that will open up a menu that displays things like the name and health and stuff of the character from the object created in CreateCharacter, but because I have it in a different class I don't know how to reference the object made in CreateCharacter.
I have it in 6 files
Character --- Object with getters/setters for things like name, age, race, class, ect
MainMenu --- Displays title and promts for new game and quit
CreateCharacter --- Walks through and sets all values in Character
Stats --- Keeps the players stats (health, attack, ect) in an array
Intro --- Beginning demo thing (not really important for this question)
Menu --- Displays all current user stats (Having issues with this one)
Example I have this in Menu
System.out.println("Name: " + ????.getName());
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